This invention relates to a machine for winding coils primarily for plastic helical bookbinding coils for insertion in the aligned holes at the edge of a book for binding the book.
It is well known that collated books are often bound using a helical coil which passes through aligned holes at one edge of the book. This provides a book which can be easily opened and held at an opened position and is therefore particularly effective for manuals and reference materials.
The helical coil at the edge of the book can be formed from a coiled wire or a coiled strip of plastic material. The coiled wire has the significant advantage that it can be more easily inserted. The helical plastic coil has the advantages that it can be manufactured in different colours and therefore provides a particularly attractive appearance as opposed to the strictly utilitarian appearance of the steel wire.
Currently helical coils are produced by rotating the plastic material on a mandrel. The material is heated in order to adopt the diameter and pitch achieved by the mandrel. Mandrels are commonly an elongate rod which has a stationary coil guide that guides the material along the rod such that the material adopts the pitch of the coil guide and the diameter of the rod. Many different sized diameters and pitches can be required by a factory producing coiled books. Currently used mandrels have to be changed with a different mandrel to produce coils with a different pitch. Mandrels can be difficult and expensive to make and if a company needs to produce many different varieties of coils they must have a different mandrel for each application.
It is one object of the present invention to provide a machine for forming helical coil from a heated elongate plastics material comprising:
an elongate cylindrical mandrel onto which the material is wrapped in helical formation which is rotatable about its longitudinal axis;
a stationary helical guide coil wrapped around the mandrel and defining a helical guide path around the mandrel between turns of the guide coil into which path the material is guided for setting into a helical shape having a diameter determined by the diameter of the mandrel and a pitch determined by the pitch of the guide coil;
at least two drive rollers parallel to the axis of the mandrel which are rotatable each about a respective longitudinal axis for applying an outer driving force to an outside of the helical coil of plastics material while it is wrapped around the mandrel and while the mandrel applies an inner driving force to the inside of the helical coil of plastics material such that the inner and outer forces tend to drive the material helically along the mandrel from a supply to a discharge end of the mandrel;
a drive coupling member at one end of the mandrel for receiving a drive from a rotatable drive member;
a mounting boss for supporting the mandrel so as to allow rotation of the mandrel while holding the mandrel against longitudinal movement;
a coil support plate having one edge attached to the turns of the helical guide coil so as to support the helical guide coil along its length with the plate extending outwardly of the axis of the mandrel;
and a support member for supporting the coil support plate at positions along its length;
the support plate being readily releasably connected to the support member so that the guide coil and the coil support plate can be removed leaving the mounting boss and support member in place for ready replacement of the guide coil by a guide coil of a different pitch.
Preferably the coil support plate has a thickness substantially equal to that of the guide coil allowing it to be welded to the guide coil.
Conveniently the support plate has a width from the edge attached to the coil to an opposed edge sufficient to define a cooling fin for applying cooling to the material on the mandrel.
Conveniently the support member is attached to the support plate at an edge opposite to the edge attached to the guide coil.
Conveniently the support member is attached to the support plate by spacer members which hold the support plate separated from the support member for allowing cooling of the support plate.
Conveniently the support member comprises an elongate bar.
Preferably the support member is attached to the mounting boss.
Preferably the drive coupling comprises a shaft having a non-circular cross-section insertable into a drive receptacle of corresponding cross-section to receive drive therefrom.
Preferably the drive coupling has a shoulder for abutting the mounting boss so that the mandrel is inserted through the mounting boss from the end opposite the drive coupling until the shoulder engages the mounting boss to hold the mandrel against longitudinal movement.
Conveniently the drive rollers consist only of two rollers arranged at opposite sides of the mandrel, each roller being mounted for movement between a drive position and a retracted position on a pivot arm with the pivot arms extending to respective pivot axes parallel to the mandrel axis and spaced outwardly from the mandrel to the same side.
Preferably the pivot arms are connected for simultaneously rotation about the respective pivot axis.
Conveniently the rollers are driven by a belt arrangement wrapped around both of the rollers, around a first pulley and a second pulley lying to the same side as the pivot axes with one pulley inwardly of and one outwardly of the pivot axes such that the rollers can pivot to the retracted position while the belt remains tensioned.
Conveniently a first of the pivot arms is pivotal by a manually operable pivot lever attached thereto and the second pivot arm is driven from the first.
Preferably there is provided an elongate cooling air supply mounted parallel to the mandrel and located at a position so as to direct air in a plane at right angles to a plane containing the drive rollers.
According to a second aspect of the invention there is provided a machine for forming helical coil from a heated elongate plastics material comprising:
an elongate cylindrical mandrel onto which the material is wrapped in helical formation which is rotatable about its longitudinal axis;
a stationary helical guide coil wrapped around the mandrel and defining a helical guide path around the mandrel between turns of the guide coil into which path the material is guided for setting into a helical shape having a diameter determined by the diameter of the mandrel and a pitch determined by the pitch of the guide coil;
at least two drive rollers parallel to the axis of the mandrel which are rotatable each about a respective longitudinal axis for applying an outer driving force to an outside of the helical coil of plastics material while it is wrapped around the mandrel and while the mandrel applies an inner driving force to the inside of the helical coil of plastics material such that the inner and outer forces tend to drive the material helically along the mandrel from a supply to a discharge end of the mandrel;
a drive coupling member at one end of the mandrel for receiving a drive from a rotatable drive member;
a mounting boss for supporting the mandrel so as to allow rotation of the mandrel while holding the mandrel against longitudinal movement;
a coil support plate having one edge attached to the turns of the helical guide coil so as to support the helical guide coil along its length with the plate extending outwardly of the axis of the mandrel;
wherein the drive rollers consist only of two rollers arranged at opposite sides of the mandrel, each roller being mounted for movement between a drive position and a retracted position on a pivot arm with the pivot arms extending to respective pivot axes parallel to the mandrel axis and spaced outwardly from the mandrel to the same side.
According to a first aspect of the invention there is provided a machine for forming helical coil from a heated elongate plastics material comprising:
an elongate cylindrical mandrel onto which the material is wrapped in helical formation which is rotatable about its longitudinal axis;
a stationary helical guide coil wrapped around the mandrel and defining a helical guide path around the mandrel between turns of the guide coil into which path the material is guided for setting into a helical shape having a diameter determined by the diameter of the mandrel and a pitch determined by the pitch of the guide coil;
at least two drive rollers parallel to the axis of the mandrel which are rotatable each about a respective longitudinal axis for applying an outer driving force to an outside of the helical coil of plastics material while it is wrapped around the mandrel and while the mandrel applies an inner driving force to the inside of the helical coil of plastics material such that the inner and outer forces tend to drive the material helically along the mandrel from a supply to a discharge end of the mandrel;
a drive coupling member at one end of the mandrel for receiving a drive from a rotatable drive member;
a mounting boss for supporting the mandrel so as to allow rotation of the mandrel while holding the mandrel against longitudinal movement;
a coil support plate having one edge attached to the turns of the helical guide coil so as to support the helical guide coil along its length with the plate extending outwardly of the axis of the mandrel;
and a cutting knife assembly for cutting the helical coil into lengths, the cutting knife assembly having;
a main body positioned at the discharge end of the mandrel opposite the mounting boss;
an opening on the main body facing the mandrel and is aligned with the axis of the mandrel;
an outer edge of the opening facing towards the axis of the mandrel;
a first portion on the outer edge having a chamfered edge for receiving the coil such that the coil is centred on the outer edge;
a second portion of the outer edge having a flat edge, and;
a cutting member being bevelled on a side facing away from the opening and a second side adjacent the opening;
the cutting member is arranged to move across the opening such that the cutting member forces the coil from the first portion to the second portion whereby the coil is cut to the desired length.
Preferably the cutting member is pivotally mounted to the main body below the opening.
Preferably the cutting member moves across the opening from side to side.
An advantage of the present invention is that the mandrel has interchangeable guide coils so that the pitch of the coil can be changed easily.